N,N-Dimethylaniline → 4-Chloro-1H-pyrazolo[3,4-d]pyrimidine

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Reaction Steps

Phosphorus oxychloride (300 mL, 3.2 mol) was added to allopurinol (Aldrich Chemical Company, Inc., Milwaukee, Wis., USA 20 g, 0.15 mol) and then N,N-dimethylaniline (30 mL, 0.24 mol) was added at room temperature. The resulting mixture was heated at reflux for 90 min and then cooled. The solvent was removed under vacuum. The residue was co-evaporated twice with toluene, and the resulting dark colored syrup was poured into a mixture of ice and water (500 mL). The mixture was stirred for 15 min, then transferred to a separatory funnel and extracted with ether (4×500 mL) and ethyl acetate (2×500 mL). The combined organic layers were washed twice with ice-water, dried (sodium sulfate), and concentrated to approximately 1.5 L. Charcoal was added to the slightly purple solution and the mixture was filtered through Celite. The Celite was washed with ethyl acetate and the combined filtrates were evaporated to dryness to give 4-chloro-1H-pyrazolo[3,4-d]pyrimidine (13 g, 56%) as a pale green solid. 1H NMR (300 MHz, DMSO-d6) δ 8.44 (s, 1H), 8.81 (s, 1H), 14.50 (br s, 1H).

Provenance & Evidence